#define _CRT_SECURE_NO_WARNINGS	

#include<stdio.h>

int main()
{
    double n;
    scanf("%lf", &n);
    double sum = 1;
    for (double i = 1; i <= n; i++)
    {
        sum *= 4 * i * i / (2 * i - 1) / (2 * i + 1);
    }
    printf("%.7f", sum * 2);
    return 0;
}